The following background information is provided to assist the reader to understand embodiments disclosed below and the environment in which they may be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise, either expressly or impliedly, in this document.
Medical devices, such as percutaneous transluminal angioplasty (PTA) balloon catheters, are often coated with various agents, including for example therapeutic agents, radiopaque materials, lubricious materials, hydrophilic materials, and biocompatible materials. PTA is a medical procedure that is used to reduce or eliminate blockages within the vascular system in order to relieve clinical symptoms associated with reduced blood flow to an organ or region of the body. PTA works by placing a non-elastomeric balloon within a blockage or narrowing and inflating it with sufficient force to restore blood flow to the distal anatomy. The balloon both compresses and expands the atherosclerotic plaque to effectively enlarge a previously constricted lumen. This procedure has become a primary therapy for treatment of occlusive vascular disease.
Unfortunately, PTA has a very high incidence of restenosis, sometimes exceeding 50%. In some circumstances, a bare metal stent (BMS) or a drug eluting stent (DES) is placed at the site of the plaque after PTA to prevent restenosis. A BMS reduces the incidence of restenosis to approximately 20% and although DES's are not currently approved for the peripheral arteries, a DES can reduce restenosis to less than 5% in the coronary arteries. While a DES is the preferred method of treatment of occlusive vascular disease (OVD) in the coronary arteries currently, problems related to late restenosis and late in-stent thrombosis have been noted with DES. In addition, the patient must remain on antiplatelet and anticoagulant therapy for an extended period of time after the procedure. Therefore, there is a need for alternate or improved therapies for the treatment of OVD. Recent therapies involve the use of drug coated PTA catheter balloons, with or without a bare metal stent, for the delivery of the drug at the lesion site to prevent restenosis.
Standard methods for coating PTA catheter balloons, such as dip coating, have several drawbacks. For example, the coating is inconsistent, non-uniform, and shreds away during handling. In addition, the process is very labor intensive, lengthy, and environmentally unfriendly. Thus, there is a continued need for improved PTA catheter balloons and methods of coating catheter balloons providing uniform and consistent delivery of effective dosages of therapeutic agents to target locations with reduced systemic dosages as well as reduced manufacturing costs.